Method for transmitting ACK/NACK signal in wireless communication system applied carrier aggregation and apparatus therefor

ABSTRACT

A method for transmitting ACK/NACK signal in a wireless communication system applied carrier aggregation is disclosed herein. More specifically, the method includes receiving multiple transmission blocks respectively through multiple downlink component carriers from a base station, determining ACK/NACK responses corresponding to each of the multiple transmission blocks by decoding the multiple transmission blocks, mapping the ACK/NACK responses to a ACK/NACK state information, and transmitting the ACK/NACK state information through a single uplink component carrier, wherein ACK information included in the ACK/NACK state information indicates a number of ACK response among the ACK/NACK responses.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending application Ser. No.13/259,060 filed Sep. 22, 2011, which is the national phase of PCTInternational Application No. PCT/KR2010/001561 filed Mar. 12, 2010,which claims priority to U.S. Provisional Applications No. 61/165,907filed Apr. 2, 2009 and 61/172,203 filed Apr. 23, 2009. The entirecontents of all of the above applications are hereby incorporated byreference.

BACKGROUND OF THE INVENTION Technical Field

The present invention relates to a wireless communication system. And,more particularly, the present invention relates to a method fortransmitting ACK/NACK signal in a wireless communication system appliedcarrier aggregation and apparatus therefor.

SUMMARY OF THE INVENTION Background Art

As an example of a wireless communication system to which the presentinvention may be applied, a 3GPP LTE (3rd Generation Partnership ProjectLong Term Evolution; hereinafter referred to as “LTE”) communicationsystem will now be broadly described.

FIG. 1 illustrates a general view of an E-UMTS network structure as anexample of a wireless communication system. Herein, the E-UMTS (EvolvedUniversal Mobile Telecommunications System) corresponds to a systemevolved from the conventional UMTS (Universal Mobile TelecommunicationsSystem). The 3GPP is presently carrying out a basic standardizationprocess for the E-UMTS. Generally, the E-UMTS may also be referred to asan LTE system. For details of the technical specifications of the UMTSand the E-UMTS, reference may be made to Release 7 and Release 8 of “3rdGeneration Partnership Project; Technical Specification Group RadioAccess Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE) (120),base stations (eNode B; eNB) 110 a and 110 b, and an Access Gateway (AG)which is located at an end of a network (E-UTRAN) and connected to anexternal network. The base stations can simultaneously transmit multipledata streams for a broadcast service, a multicast service and/or aunicast service.

One or more cells may exist for one base station. One cell is set to oneof bandwidths of 1.25, 2.5, 5, 10, and 20 Mhz to provide a downlink oruplink transport service to several user equipments. Different cells maybe set to provide different bandwidths. Also, one base station controlsdata transmission and reception for a plurality of user equipments. Thebase station transmits Downlink (DL) scheduling information of downlinkdata to the corresponding user equipment to notify information relatedto time and frequency domains to which data will be transmitted,encoding, data size, and HARQ (Hybrid Automatic Repeat and reQuest).Also, the base station transmits Uplink (UL) scheduling information ofuplink data to the corresponding user equipment to notify informationrelated to time and frequency domains that can be used by thecorresponding user equipment, encoding, data size, and HARQ. Aninterface for transmitting user traffic or control traffic can be usedbetween the base stations. A Core Network (CN) may include the AG and anetwork node or the like for user registration of the UE. The AG managesmobility of a UE on a TA (Tracking Area) basis, wherein one TA includesa plurality of cells.

The wireless communication technology has been developed up to the LTEbased upon WCDMA. However, the demands and expectations of the users andthe manufacturers and providers are growing continuously. Also, sinceother wireless access technologies are constantly being developed, thewireless communication technology is required to newly evolve in orderto ensure competiveness in the future. Accordingly, characteristics,such as reduced cost for each bit, increased service availability, usageof a flexible frequency band, simple structure and open interface, andadequate power consumption of the user equipment are being requested.

Recently, a standardization procedure for a succeeding (or subsequent)technology of the LTE has been under progress by the 3GPP. In thedescription of the present invention, the above-mentioned technologywill be referred to as “LTE-Advanced” or “LTE-A”. The essentialdifference between the LTE system and the LTE-A system is the systembandwidth. The LTE-A system aims to support a broadband of up to 100MHz. For this, the LTE-A system encourages the use of a carrieraggregation (or bandwidth aggregation) technology, which achieves abroadband by using multiple component carriers. In order to use a wider(or broader) frequency band, the carrier aggregation (or bandwidthaggregation) uses a plurality of component carriers as a single largelogical frequency band. The bandwidth of each component carrier (orbandwidth carrier) may be defined based upon the bandwidth of a systemblock used in the LTE system. Each component carrier (or bandwidthcarrier) uses a component carrier (or bandwidth carrier) so as to betransmitted.

DISCLOSURE Technical Problem

The present invention is devised to provide a method for transmitting acontrol signals and an apparatus of the same in a wireless communicationsystem. Also, the present invention is devised to provide a method fortransmitting ACK/NACK signal in a wireless communication system appliedcarrier aggregation and apparatus therefore.

The technical objectives that are to be realized by the presentinvention will not be limited only to the technical objects pointed outherein. Other technical objectives that have not yet been mentionedherein will become apparent to those having ordinary skill in the artupon examination of the following or may be learned from practice of theinvention.

Technical Solution

In an aspect of the present invention, a method for transmittingACK/NACK (Acknowledgement/Negative-ACK) state information in a wirelesscommunication system includes receiving multiple transmission blocksrespectively through multiple downlink component carriers from a basestation; determining ACK/NACK responses corresponding to each of themultiple transmission blocks by decoding the multiple transmissionblocks; mapping the ACK/NACK responses to a ACK/NACK state information;and transmitting the ACK/NACK state information through a single uplinkcomponent carrier, wherein ACK information included in the ACK/NACKstate information indicates a number of ACK response among the ACK/NACKresponses. Herein, NACK information included in the ACK/NACK stateinformation may indicate a case where decoding of the multipletransmission blocks all failed.

Also, in the receiving multiple transmission blocks, two or moretransmission blocks may be received through at least one downlinkcomponent carrier among the multiple downlink component carriers.

Preferably, the step of mapping to the ACK/NACK state information mayinclude a step of mapping a predetermined number of ACK/NACK responsesamong the ACK/NACK responses to the ACK/NACK state information. Also,the step of transmitting the ACK/NACK state information to the basestation may include transmitting the ACK/NACK state information by usingone or more PUCCH (Physical Uplink Control CHannel) resources includedin the one uplink component carrier.

More preferably, the step of transmitting to the base station mayfurther include modulating the ACK/NACK state information using QPSK(Quadrature Phase Shift Keying).

In another aspect of the present invention, a user equipment includes areceiving module for receiving multiple transmission blocks respectivelythrough multiple downlink component carriers from a base station; aprocessor for determining ACK/NACK responses corresponding to each ofthe multiple transmission blocks by decoding the multiple transmissionblocks, and for mapping the ACK/NACK responses to a ACK/NACK stateinformation; and a transmitting module for transmitting the ACK/NACKstate information through a single uplink component carrier, wherein ACKinformation included in the ACK/NACK state information indicates anumber of ACK response among the ACK/NACK responses. Herein, NACKinformation included in the ACK/NACK state information may indicate acase where decoding of the multiple transmission blocks all failed.

The receiving module may receive two or more transmission blocks throughat least one downlink component carrier among the multiple downlinkcomponent carriers. And, the processor may map a predetermined number ofACK/NACK responses among the ACK/NACK responses to the ACK/NACK stateinformation.

Also, the transmitting module may transmit the ACK/NACK stateinformation by using one or more PUCCH (Physical Uplink Control CHannel)resources included in the one uplink component carrier. And, theprocessor may modulate the ACK/NACK state information using QPSK(Quadrature Phase Shift Keying).

Advantageous Effects

According to the embodiments of the present invention, in a wirelesscommunication system applying carrier aggregation, the ACK/NACK signalmay be efficiently transmitted.

The effects that can be achieved in the present invention will not belimited only to the effects pointed out in the description of thepresent invention. Other effects that have not yet been mentioned hereinwill become apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andalong with the description serve to explain the spirit and scope (orprinciple) of the invention.

FIG. 1 illustrates a general view of an E-UMTS network structure as anexample of a wireless communication system.

FIG. 2 illustrates block views of a transmitter and a receiver for OFDMAand SC-FDMA.

FIG. 3 illustrates an exemplary structure of a wireless frame used inthe LTE.

FIG. 4 illustrates an example of performing communication in a singlecomponent carrier condition.

FIG. 5 illustrates an exemplary uplink sub-frame used in the LTE.

FIG. 6 illustrates an exemplary PUCCH structure for transmittingACK/NACK.

FIG. 7 illustrates an example of deciding a PUCCH resource fortransmitting an ACK/NACK signal.

FIG. 8 illustrates an example of performing communication under amultiple component carrier condition.

FIG. 9 illustrates an exemplary application of an asymmetrical carrieraggregation (or bandwidth aggregation) in an LTE-A system.

FIG. 10 illustrates a method for transmitting an ACK/NACK signal byusing two PUCCH resources and one antenna according to an embodiment ofthe present invention.

FIG. 11 illustrates a method for transmitting an ACK/NACK signal in auser terminal through two PUCCH resources and two respective antennae.

FIG. 12 illustrates an exemplary base station and an exemplary userterminal that can be applied to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS Mode for Invention

Hereinafter, the structure, operation, and other characteristicsaccording to the preferred embodiments of the present invention will nowbe described in detail with reference to the accompanying drawings andthe details given in the accompanying drawings. Hereinafter, thepreferred embodiments of the present invention correspond to exampleswherein the technical characteristics of the present invention areapplied in a 3GPP system.

Hereinafter, a system, wherein the system band uses a single componentcarrier, will be referred to as a legacy system or a narrowband system.Respectively, a system, wherein the system band includes multiplecomponent carriers, and wherein at least one or more component carriersare used as a system block of a legacy system, will be referred to as anevolved system or a wideband system. A component carrier used as alegacy system block has the same size as that of a system block oflegacy system. Conversely, the sizes of the remaining componentscarriers are not particularly limited. However, in order to simplify thesystem, the sizes of the remaining component carriers may also bedecided based upon the system block size of the legacy system. Forexample, the relation between a 3GPP LTE system and a 3GPP LTE-A systemcorresponds to a relation between a legacy system and an evolved system.

Based upon the above-described definition, the 3GPP LTE system will bereferred to as an LTE system or a legacy system in the description.Also, a user equipment supporting the LTE system will be referred to asan LTE user equipment (or terminal) or a legacy user equipment (orterminal). Respectively, the 3GPP LTE-A system will be referred to as anLTE-A system or an evolved system in the description. Also, a userequipment supporting the LTE-A system will be referred to as an LTE-Auser equipment (or terminal) or an evolved user equipment (or terminal).

In the description of the present invention, the LTE system and theLTE-A system are used to describe the embodiments of the presentinvention, for simplicity. However, this is merely exemplary, and theembodiments of the present invention may be applied to any communicationsystem corresponding to the above definition.

FIG. 2 illustrates block views of a transmitter and a receiver for OFDMAand SC-FDMA. In an uplink, a transmitter (202˜214) is a user terminal,and a receiver (216˜230) is a portion of a base station. In a downlink,the transmitter is a portion of the base station, and the receiver is aportion of the user terminal.

Referring to FIG. 2, an OFDMA transmitter includes a Serial to Parallelconverter (202), a sub-carrier mapping module (206), an M-point IDFT(Inverse Discrete Fourier Transform module (208), a Cyclic prefix (CP)adding module (210), a Parallel to Serial converter (212), and an RF(Radio Frequency)/DAC (Digital to Analog Converter) module (214).

In the OFDMA transmitter, a signal processing procedure is as describedbelow. Firstly, a bit stream is modulated to a data symbol sequence. Thebit stream may be obtained by performing diverse signal processing, suchas channel encoding, interleaving, scrambling, and so on, on a datablock received (or delivered) from a Medium Access Control (MAC) layer.The bit stream may also be referred to as a codeword and is equivalentto a data block received from the MAC layer. The data block receivedfrom the MAC layer may also be referred to as a transmission block.Although the modulation method of the present invention will not belimited to the following examples, the modulation method may includeBPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying),and n-QAM (Quadrature Amplitude Modulation). Subsequently, a serial datasymbol sequence is converted in parallel by N number of units (202). Nnumber of data symbols is mapped to N number of sub-carriers, which isassigned from a total of M number of sub-carriers. Then, the remainingM-N number of sub-carriers is padded to 0 (206). The data symbols mappedto a frequency domain are converted to a time domain sequence viaM-point IDTF processing (208). Thereafter, in order to reduceInter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI), aCP is added to the time domain sequence, thereby generating an OFDMAsymbol (210). The generated OFDMA symbol is converted from parallel toserial (212). Afterwards, the OFDMA symbol is processed with proceduressuch as digital-to-analog conversion, frequency uplink conversion, so asto be transmitted (or delivered) to the receiver (214). Another user isassigned with available sub-carriers among the remaining M-N number ofsub-carriers. An OFDMA receiver includes an RF/ADC (Analog to DigitalConverter) module (216), a Serial to Parallel converter (218), a RemoveCP module (220), an M-point DFT (Discrete Fourier Transform) module(222), a sub-carrier demapping/equalization module (224), a Parallel toSerial converter (228), and a detection module (230). The signalprocessing procedure of the OFDMA receiver is configured as an inverseprocedure of the OFDMA transmitter.

In comparison with the OFDMA transmitter, an SC-FDMA transmitteradditionally includes an N-point DFT module (204) before the sub-carriermapping module (206). Prior to IDTF processing, the SC-FDMA transmitterdisperses multiple data to the frequency domain through DFT, therebybeing capable of reducing a PAPR (Peak-to-Average Power Ratio) of thetransmitting signal, as compared to the PFDMA method. In comparison withthe OFDMA receiver, an SC-FDMA receiver additionally includes an N-pointIDFT module (226) after the sub-carrier demapping/equalization module(224). The signal processing procedure of the SC-FDMA receiver isconfigured as an inverse procedure of the SC-FDMA transmitter.

FIG. 3 illustrates an exemplary structure of a wireless frame used inthe LTE.

Referring to FIG. 3, a radio frame has the length of 10 ms(327200·T_(s)) and is configured of 10 subframes each having the samesize. Each subframe has the length of 1 ms and is configured of 2 slots.Each slot has the length of 0.5 ms (15360·T_(s)). Herein, T_(s)represents a sampling time and is indicated as T_(s)=1/(15kHz×2048)=3.2552×10⁻⁸ (approximately 33 ns). A slot includes multipleOFDMA (or SC-FDMA) symbols in the time domain and includes multipleResource Blocks (RBs) in the frequency domain. In the LTE system, oneresource block includes 12 subcarriers×7(6) OFDMA (or SC-FDMA) symbols.A Transmission Time Interval (TTI), which corresponds to a time unit atwhich the data are transmitted, may be decided as one or more subframeunits. The above-described structure of the radio frame is merelyexemplary. And, therefore, the number of subframes within a radio frame,the number of slots within a subframe, and the number of OFDMA (orSC-FDMA) symbols within a slot may be diversely modified.

FIG. 4 illustrates an example of performing communication in a singlecomponent carrier condition. FIG. 4 may correspond to a communicationexample of the LTE system. In an FDD (Frequency Division Duplex) method,data transmission and reception may be performed via one downlink bandand one uplink band respective to the downlink band. More specifically,in the FDD method, the radio frame structure of FIG. 4 is used only in adownlink transmission or an uplink transmission. Conversely, in a TDD(Time Division Duplex) method, the same frequency band is divided into adownlink section and an uplink section respective to the downlinksection. More specifically, in the TDD method also, the radio framestructure of FIG. 4 is used only in a downlink transmission or an uplinktransmission.

Referring to FIG. 4, a method of performing an HARQ (Hybrid AutomaticRepeat and reQuest) procedure by the user equipment (or terminal) willbe described in detail. In the LTE system, a control information on adownlink data transmission of the base station (e.g., a schedulinginformation) is transmitted (or delivered) through a downlink controlchannel predetermined in a control region of the downlink subframe. Thedownlink control channel includes a PDCCH (Physical Downlink ControlChannel). The user equipment first receives the scheduling information(e.g., resources assigned with data, the size of the data, the codingmethod, the redundancy version, etc.) through the control channel andmay, then, receive scheduled data through a downlink shared channel,which is indicated (or designated) by the scheduling information.

The downlink shared channel includes a PDSCH (Physical Uplink Channel).Subsequently, the user equipment may transmit a reception responsesignal (e.g., HARQ ACK/NACK) for the downlink data through an uplinkcontrol channel predetermined within the control region of the uplinksubframe. The uplink control channel includes a PUCCH (Physical UplinkControl Channel). In the description of the present invention, the HARQACK/NACK will be simply indicated as ACK/NACK signal for simplicity. Thebase station receives the ACK/NACK signal from the user equipment. Then,the base station performs retransmission of the downlink data designatedas NACK. When the base station transmits multiple downlink data to theuser equipment, the HARQ procedure may be performed for eachtransmission block respective to each downlink data.

FIG. 5 illustrates an exemplary uplink sub-frame used in the LTE.

Referring to FIG. 5, the uplink subframe includes a plurality (e.g., 2)slots. Depending upon the CP length, each slot may include a differentnumber of SC-FDMA symbols. For example, in case of a normal CP, a slotmay include 7 SC-FDMA symbols. The uplink subframe is divided intro adata region and a control region. The data region includes the PUSCH andis used for transmitting data signals, such as audio signals. Thecontrol region includes the PUCCH and is used for transmitting controlinformation. The PUCCH includes an RB pair (e.g., m=0, 1, 2, 3)positioned at each end of the data region along a frequency axis. And,the PUCCH performs hopping at slot boundaries. The control informationincludes ACK/NACK, CQI, PMI, RI, and so on.

FIG. 6 illustrates an exemplary PUCCH structure for transmittingACK/NACK.

Referring to FIG. 6, in case of a normal CP, a reference signal (UL RS)is carried (or contained) in contiguous (or consecutive) symbolspositioned in the middle of the slot, and control information (i.e.,ACK/NACK) is carried (or contained) in the remaining 4 symbols. In caseof an extended CP, a slot includes 6 symbols, among which the 3^(rd) and4^(th) symbols are carried (or contained) in the reference signal. TheACK/NACK received from multiple user equipments are multiplexed in onePUCCH resource by using a CDM method. The CDM method is realized byusing a Cyclic Shift (CS) of a sequence for frequency distribution (ordispersion) and/or a (semi-)orthogonal dispersion code for timedispersion. For example, the ACK/NACK is differentiated by usingdifferent Cyclic Shifts (CSs) of a CG-CAZAC (Computer Generated ConstantAmplitude Zero Auto Correlation) sequence (frequency dispersion) and/orby using different Walsh/DFT orthogonal codes (time dispersion). Theresult of multiplying by w0, w1, w2, w3 after the IFFT is identical tothe result of multiplying w0, w1, w2, w3 prior to the IFFT. In the LTEsystem, the PUCCH resource for transmitting the ACK/NACK is expressed asa combination of the frequency-time resource (e.g., resource block)position, the cyclic shift of a sequence for frequency dispersion, andthe (semi-)orthogonal dispersion code for time dispersion. Herein, eachPUCCH resource is designated by using a PUCCH (resource) index.

FIG. 7 illustrates an example of deciding a PUCCH resource fortransmitting an ACK/NACK signal. In the LTE system, a PUCCH resource forthe ACK/NACK is not assigned to each user equipment in advance, and,instead, the multiple user equipments share the multiple PUCCH resourcesat each time point. More specifically, the PUCCH resource used by theuser equipment to transmit the ACK/NACK corresponds to a PDCCH, whichcarries and delivers scheduling information on the respective downlinkdata. The entire region, wherein the PDCCH is transmitted from eachdownlink subframe, is configured of multiple CCEs (Control ChannelElements). And, the PDCCH being transmitted to the user equipment isconfigured of one or more CCEs. Among the PDCCH received by the userequipment, the user equipment transmits an ACK/NACK through a PUCCHresource corresponding to a specific CCE (e.g., first CCE).

Referring to FIG. 7, in a DownLink Component Carrier each squareindicates a CCE, and in an UpLink Component Carrier (UL CC) each squarerepresents a PUCCH resource. Each PUCCH index corresponds to a PUCCHresource for the ACK/NACK. As shown in FIG. 7, when it is assumed thatinformation on a PDSCH is being delivered through a PDCCH configured ofCCE number 4˜6, the user equipment transmits the ACK/NACK through PUCCHnumber 4, which corresponds to CCE number 4, the CCE number 4 being thefirst CCE configuring the PDCCH. FIG. 6 is an exemplary case where amaximum of M number of PUCCHs exists in a UL CC, when a maximum of Nnumber of CCEs exist in the DownLink Component Carrier. Although N maybe equal to M (N=M), the M value and the N value may be differentlyset-up, and the mapping of the CCEs and the PUCCHs may be set to overlapone another.

More specifically, in the LTE system, a PUCCH resource index is decidedas shown below.n ⁽¹⁾ _(PUCCH) =n _(CCE) +N ⁽¹⁾ _(PUCCH)  [Equation 1]

Herein, n⁽¹⁾ _(PUCCH) represents a PUCCH resource index for transmittingthe ACK/NACK, N⁽¹⁾ _(PUCCH) indicates a signaling value received from anupper layer, and n_(CCE)

represents a smallest value among a CCE index used in a PDCCHtransmission.

FIG. 8 illustrates an example of performing communication under amultiple component carrier condition. FIG. 8 may correspond to acommunication example of an LTE-A system. In order to use a widerfrequency bandwidth, the LTE-A system adopts a carrier aggregation (orbandwidth aggregation) technology gathering a plurality of up-/downlinkfrequency blocks, so as to use a larger (or wider) up-/downlinkbandwidth. Each frequency block is transmitted by using a ComponentCarrier (CC).

Referring to FIG. 8, 5 20 MHz CCs may be gathered in each of theup-/downlink, so as to support a 100 MHz bandwidth. The ComponentCarriers may be adjacent or non-adjacent to one another in the frequencydomain. The radio frame structure shown in FIG. 3 may be identicallyapplied to a case where multiple component carriers are being used.However, since the radio frame, the subframe, and the slot correspond totime units, the base station and the user equipment may, for example,transmit and receive a signal through the plurality of componentcarriers within a single subframe. FIG. 8 shows an example where thebandwidth of the uplink component carrier and the bandwidth of thedownlink component carrier are identical to one another and aresymmetrical to one another. However, the bandwidth of each componentcarrier may be decided independently. For example, the bandwidth of theuplink component carrier may be configured as 5 MHz (UL CC0)+20 MHz (ULCC1)+20 MHz (UL CC2)+20 MHz (UL CC3)+5 MHz (UL CC4). Also, anasymmetrical carrier aggregation (or bandwidth aggregation), wherein thenumber of UL CCs and the number of downlink component carriers aredifferent from one another, may be used. The asymmetrical carrieraggregation (or bandwidth aggregation) may be generated due to alimitation in the available frequency band, or may be artificiallyconfigured by network settings. Also, although it is shown, as anexample, that the uplink signal and the downlink signal are transmittedthrough a component carrier mapped at a one-to-one (1:1) correspondencewith the signal, the component carrier through which a signal isactually being transmitted may vary depending upon the network settingsor the signal type. For example, a component carrier transmitting ascheduling command and a component carrier transmitting data inaccordance with a scheduling command may be different from one another.Furthermore, up-/downlink control information may be transmitted throughspecific uplink/downlink component carrier, regardless of the mappingstate between the component carriers.

Although the present invention is not limited to this, when the numberof uplink component carriers is smaller than the number of downlinkcomponent carriers, the ACK/NACK for the transmission of a plurality ofdownlink PDSCHs should be transmitted through a smaller number of uplinkPUCCHs. Particularly, settings may be made so that the ACK/NACK for thetransmission of a plurality of downlink PDSCHs is transmitted onlythrough a specific uplink component carrier. Also, even when the numberof uplink component carriers is the same as the number of downlinkcomponent carriers, when a MIMO (Multiple Input Multiple Output)transmission method is used, or when operated via TDD, the userequipment received a plurality of transmission blocks. In this case, theuser equipment should transmit the ACK/NACK signal for multipletransmission blocks through limited PUCCH resources.

FIG. 9 illustrates an exemplary application of an asymmetrical carrieraggregation (or bandwidth aggregation) in an LTE-A system. Particularly,FIG. 9 shows an example wherein a plurality of transmission blocks isreceived through 3 downlink component carriers, and wherein therespective ACK/NACK signals are transmitted through a single uplinkcomponent carrier.

If 2 transmission blocks are transmitted to the user equipment througheach of the downlink component carriers, the user equipment shouldfeed-back 6 ACK/NACK signals to the base station a single uplinkcomponent carrier. When it is assumed that a single PUCCH resource isinsufficient for transmitted multiple ACK/NACK signals, the userequipment may assign multiple PUCCH resources so as to transmit multipleACK/NACK signals. However, due to a limited amount of transmission powerin the user equipment, the assigning of the multiple PUCCH resources maycause problems, such as worsening (or aggravating) the PAPR or CM andalso increasing interference between the PUCCHs.

In order to resolve such problems, an ACK/NACK bundling method isproposed. Herein, the ACK/NACK bundling method corresponds to a methodof combining ACK/NACK signals for multiple data by using a logical ANDoperation. For example, ACK may be transmitted only when the receivingend has successfully decoded all data. And, other cases indicate that aNACK signal is transmitted or no signal is transmitted at all. However,in the related art ACK/NACK bundling method, although an overallACK/NACK signal feedback overhead is reduced, there still remains aproblem in that a re-transmission overhead increases in the basestation.

Hereinafter, an ACK/NACK bundling method enabling the user equipment toefficiently transmit ACK/NACK signals through a single uplink componentcarrier, the user equipment having received transmission blocks throughmultiple downlink component carriers, in a wireless communication systemapplying carrier aggregation (or bandwidth aggregation), such as in theLTE-A system, is proposed.

<When the Base Station Operates in a Non-MIMO Mode>

Firstly, when the base station is in a Non-MIMO mode, i.e., when onlyone transmission block is transmitted through one component carrier, amethod of bundling ACK/NACK signals by using one PUCCH resource and amethod of bundling ACK/NACK signals by using two PUCCH resources, in auser equipment, will be described.

a) Method of Bundling ACK/NACK Signals by Using One PUCCH Resource

In case only one PUCCH is being used, and when a case of nottransmitting any signal is also considered, the BPSK may indicate amaximum of 3 ACK/NACK states, the QPSK may indicate a maximum of 5ACK/NACK states, and the 8PSK may indicate a maximum of 9 ACK/NACKstates. Based upon the maximum number of ACK/NACK states that can beindicated in accordance with a modulation order, an example of bundlingACK/NACK signals by using a single PUCCH resource, thereby mapping thebundled signal to ACK/NACK state information is shown in Table 1 below.

TABLE 1 # of downlink CCs or # of ACK/NACK State definition; over Note:ACKn means multiple number of ACK equal Example CCs to n Modulationmapping; 1 ACK, NACK, DTX BPSK ACK(1), NACK(0), DTX(no Tx) ACK(1),NACK/DTX(no Tx) 2 ACK1, ACK2, NACK, BPSK ACK1(1), DTX ACK2(0), NACK/DTX(no Tx) QPSK ACK1(01), ACK2(10), NACK(11), DTX(no Tx) 3 ACK1, ACK2,ACK3, QPSK ACK1(01), NACK, DTX ACK2(10), ACK3(11), NACK(00), DTX(no Tx)ACK1(01), ACK2(10), ACK3(11), NACK/DTX(no Tx) 4 ACK1, ACK2, ACK3, QPSKACK1(00), ACK4, NACK, DTX ACK2(01), ACK3(10), ACK4(11), NACK/DTX(no Tx)8PSK ACK1(000), ACK2(001), ACK3(010), ACK4(011), NACK(100), DTX(no Tx) 5ACK1, ACK2, ACK3, 8PSK ACK1(000), ACK4, ACK5, NACK, ACK2(001), DTXACK3(010), ACK4(011), ACK5(100), [NACK(101), DTX(no Tx)] or [NACK/DTX(noTx)] ACK[1~2], ACK3, QPSK ACK[1~2](00), ACK4, ACK5, NACK, ACK[3](01),DTX ACK4(10), ACK5(11), NACK/DTX(no Tx) 6 ACK1, ACK2, ACK3, 8PSKACK1(000), ACK4, ACK5, ACK6, ACK2(001), NACK, DTX ACK3(010), ACK4(011),ACK5(100), ACK6(101), [NACK(110), DTX(no Tx)] or [NACK/DTX(no Tx)]ACK[1~2], ACK[3~4], QPSK ACK[1~2](00), ACK5, ACK6, NACK, ACK[3~4](01),DTX ACK5(10), ACK6(11), NACK/DTX(no Tx) 7 ACK1, ACK2, ACK3, 8PSKACK1(000), ACK4, ACK5, ACK6, ACK2(001), ACK7, NACK, DTX ACK3(010),ACK4(011), ACK5(100), ACK6(101), ACK7(110), [NACK(111), DTX(no Tx)] or[NACK/DTX(no Tx)] ACK[1~2], ACK[3~4], QPSK ACK[1~2](00), ACK[5~6], ACK7,ACK[3~4](01), NACK, DTX ACK[5~6](10), ACK7(11), NACK/DTX(no Tx) 8 ACK1,ACK2, ACK3, 8PSK ACK1(000), ACK4, ACK5, ACK6, ACK2(001), ACK7, ACK8,NACK, ACK3(010), DTX ACK4(011), ACK5(100), ACK6(101), ACK7(110),ACK8(111), NACK/DTX(no Tx) ACK[1~2], ACK[3~4], QPSK ACK[1~2](00),ACK[5~6], ACK[7~8], ACK[3~4](01), NACK, DTX ACK[5~6](10), ACK[7~8](11),NACK/DTX(no Tx)

In Table 1, ACKn signifies a state information indicating that accordingto a result of decoding transmission blocks received by the userterminal through a downlink component carrier, the number of ACKs isequal to n, and, as a decoding result, ACK[x˜y] represents the stateinformation indicating that the number of ACKs is between x and y numberof state information.

Referring to Table 1, it is apparent that the state information of thebundled ACK/NACK indicates how many ACKs are included. In case a NACK isbeing reported, since this indicates that eventually all data areretransmitted, it should be noted that there is no difference betweenthe state information and the reporting of a non-reception of PDCCH,i.e., DTX. If the NACK and DTX are differentiated, and if the mappingpoints are insufficient, a method of grouping a specific number ofACK/NACK state information, such as ACK[x˜y], may be taken intoconsideration. In this case, it is preferable to gather ACK/NACK stateinformation that can relatively occur less. For example, if theprobability of successfully decoding multiple transmission blocks isrelatively greater than the probability of failing to decode thetransmission block, the ACK/NACK state information having smaller ACKnumbers may be bundled. Therefore, when receiving 8 transmission blocksthrough 8 downlink carriers, the ACK/NACK state information may bedefined such as ACK[1˜4], ACK5, ACK6, ACK7, and ACK8.

b) Method of Bundling ACK/NACK Signals by Using Two PUCCH Resources

FIG. 10 illustrates a method for transmitting an ACK/NACK signal byusing two PUCCH resources and one antenna according to an embodiment ofthe present invention. Also, in FIG. 10, it should be noted that onlyone of two PUCCH resources are used for transmitting an ACK/NACK signal.

Referring to FIG. 10, when two PUCCH resources are used to feed-back theACK/NACK state information, the ACK/NACK state may be defined by 3factors, ID of the PUCCH resource, modulation value, and DTX(non-transmission). An example of bundling ACK/NACK signals by using twoPUCCH resources, thereby mapping the bundled signal to ACK/NACK stateinformation is shown in Table 2 below.

TABLE 2 # of downlink CCs or # of ACK/ Example mapping; NACK Statedefinition; Note: PUCCH over Note: ACKn means resource is multiplenumber of ACK denoted as ra or CCs equal to n Modulation rb. 1 ACK,NACK, DTX Same with Table 1 with one PUCCH resource 2 ACK1, ACK2, Samewith Table 1 with one NACK, DTX PUCCH resource 3 ACK1, ACK2, ACK3, Samewith Table 1 with one NACK, DTX PUCCH resource BPSK ACK1(ra, 0),ACK2(ra, 1), ACK3(rb, 0), [NACK(rb, 1), DTX(no Tx)] or [NACK/DTX(no Tx)]4 ACK1, ACK2, ACK3, Same with Table 1 with one ACK4, NACK, DTX PUCCHresource BPSK ACK1(ra, 0), ACK2(ra, 1), ACK3(rb, 0), ACK4(rb, 1), NACK/DTX(no Tx) 5 ACK1, ACK2, ACK3, QPSK/BPSK ACK1(ra, 00), ACK4, ACK5,ACK2(ra, 01), NACK, DTX ACK3(ra, 10), ACK4(ra, 11), ACK5(rb, 0),[NACK(rb, 1), DTX(no Tx)] or [NACK/DTX(no Tx)] ACK1(ra, 00), ACK2(ra,01), ACK3(ra, 10), [ACK4(ra, 11), ACK5(rb, 0), NACK(rb, 1), DTX(no Tx)]or [ACK4(rb, 1), ACK5(rb, 0), NACK/ DTX(no Tx)] 6 ACK1, ACK2, ACK3,QPSK/BPSK ACK1(ra, 00), ACK4, ACK5, ACK6, ACK2(ra, 01), NACK, DTXACK3(ra, 10), ACK4(ra, 11), [ACK5(rb, 00), ACK6(rb, 01), NACK(rb, 10),DTX(no Tx)] or [ACK5(rb, 0), ACK6(rb, 1), NACK/ DTX(no Tx)] 7 ACK1,ACK2, ACK3, QPSK ACK1(ra, 00), ACK4, ACK5, ACK6, ACK2(ra, 01), ACK7,NACK, DTX ACK3(ra, 10), ACK4(ra, 11), ACK5(rb, 00), ACK6(rb, 01),ACK7(rb, 10), [NACK(rb, 11), DTX(no Tx)] or [NACK/DTX(no Tx)] 8 ACK1,ACK2, ACK3, QPSK ACK1(ra, 00), ACK4, ACK5, ACK6, ACK2(ra, 01), ACK7,ACK8, ACK3(ra, 10), NACK, DTX ACK4(ra, 11), ACK5(rb, 00), ACK6(rb, 01),ACK7(rb, 10), ACK8(rb, 11), NACK/DTX(no Tx) 9 ACK1, ACK2, ACK3,QPSK/8PSK ACK1(ra, 001), ACK4, ACK5, ACK6, ACK2(ra, 010), ACK7, ACK8,ACK9, ACK3(ra, 100), NACK, DTX ACK4(ra, 110), ACK5(ra, 000), ACK6(rb,01), ACK7(rb, 10), ACK8(rb, 11), ACK9(rb, 00), NACK/DTX(no Tx) ACK[1~2],ACK3, QPSK ACK[1~2](ra, 00), ACK4, ACK5, ACK6, ACK3(ra, 10), ACK7, ACK8,ACK9, ACK4(ra, 11), NACK, DTX ACK5(ra, 01), ACK6(rb, 01), ACK7(rb, 10),ACK8(rb, 11), ACK9(rb, 00), NACK/DTX(no Tx) 10 ACK1, ACK2, ACK3,QPSK/8PSK ACK1(ra, 001), ACK4, ACK5, ACK6, ACK2(ra, 010), ACK7, ACK8,ACK9, ACK3(ra, 100), ACK10, NACK, DTX ACK4(ra, 110), ACK5(ra, 000),ACK6(rb, 001), ACK7(rb, 100), ACK8(rb, 110), ACK9(rb, 000), ACK10(rb,010), NACK/DTX(no Tx) ACK[1~2], QPSK ACK[1~2](ra, 00), ACK[3~4], ACK5,ACK[3~4](ra, 10), ACK6, ACK7, ACK8, ACK5(ra, 11), ACK9, ACK10, ACK6(ra,01), NACK, DTX ACK7(rb, 01), ACK8(rb, 10), ACK9(rb, 11), ACK10(rb, 00),NACK/DTX(no Tx)

Generally, in the aspect of reliability, the QPSK shows a betterperformance than the 8PSK. Therefore, it is apparent that the 8PSKmethod is used for transmitting a large number of ACK/NACK signals, suchas when transmitting 9 or 10 ACK/NACK signals.

Also, even when indicating the ACK/NACK state information in a bundle,it is preferable to bundle (or gather) cases that can occur relativelyless. Therefore, when 10 transmission blocks are received through 10downlink carriers, since the probability of successfully performingdecoding is relatively greater than the probability of failing toperform decoding, the ACK/NACK state information may be defined asACK[1˜3], ACK4, ACK5, ACK6, ACK7, ACK8, ACK9, and ACK10.

<When the Base Station Operates in a MIMO Mode>

If the base station is operated in a MIMO mode, the space domain is alsorequired to be taken into consideration for the ACK/NACK bundling. Morespecifically, when 2 transmission blocks are received through a singledownlink component carrier, the ACK/NACK state information may alsoinclude the index of each transmission block as its factor.

However, since the application of the MIMO mode may differ for each ofthe downlink component carriers, it is preferable that the ACK/NACKstate information is defined based upon a maximum number of transmissionblocks that can be transmitted through the downlink component carrier.

Additionally, depending upon whether or not an uplink transmission of auser equipment is operated in the MIMO mode, the ACK/NACK bundlingmethod may differ.

a) When the Uplink Transmission of the User Equipment is in a Non-MIMOMode

In case the base station transmits each of the multiple transmissionblocks through a respective downlink component carrier, and in case theuser equipment transmits a single uplink component carrier as a responseto the above through a single antenna, the ACK/NACK state informationmay be defined as shown in Table 3 below. Particularly, it is assumed inTable 3 that two transmission blocks are received through a singledownlink component carrier.

TABLE 3 # Example Mapping; of # of Note: PUCCH resource is DL BundledACK/NACK PUCCH denoted as rk, where n can CCs state resources be 1 to n.1~5 ACKA[1~5], ACKB[1~5], 1 (ACKA[1~5], ACKB[1~5]) = (00), NACKA, DTXNACKB, DTX (NACKA, ACKB[1~5]) = (01), (ACKA[1~5], NACKB) = (10), (NACKA,NACKB) = (11), DTX(no Tx) n ACKA[k], ACKB[k], <=n (ACKA[k], ACKB[k]) =(rk, 00), NACKA, NACKB, (NACKA, ACKB[k]) = (rk, 01), DTX, DTX, (ACKA[k],NACKB) = (rk, 10), k = 1, 2, . . . , 5 k = 1, 2, . . . , 5 (NACKA,NACKB) = (rk, 11), DTX(no Tx)

In Table 3, ACKA[1˜5] indicates that the decoding result of thetransmission block A received through the downlink component carrierscorresponds to ACK, and ACKB[1˜5] indicates that the decoding result ofthe transmission block B received through the downlink componentcarriers corresponds to ACK.

If the modulation method is limited to the QPSK as shown in Table 3, itis apparent that in order to express (or indicate) the number of allACKs that can be generated, a number of PUCCH resources corresponding tothe number of downlink component carriers is required. Also, if thenumber of PUCCH resources is smaller than the number of downlinkcomponent carriers, it is preferable to bundle (or gather) ACK/NACKstates that can be generated relatively more, as shown in Table 1 andTable 2, in order to reduce the number of ACK/NACK state information.

b) When the Uplink Transmission of the User Equipment is in an MIMO Mode

FIG. 11 illustrates a method for transmitting an ACK/NACK signal in auser terminal through two PUCCH resources and two respective antennae.

In case the user equipment performs uplink transmission by usingmultiple antennae, a method of defining ACK/NACK state information basedupon the transmission block, by primarily performing the methods shownin Table 1 and Table 2 from each antenna, may be taken intoconsideration.

Also, when the number of transmission blocks being received through eachdownlink component carrier is the same, the ACK/NACK state informationmay be defined as shown in Table 4 below. Most particularly, in Table 4,it is assumed that 2 transmission blocks are received through a singledownlink component carrier and that an uplink modulation method islimited to QPSK.

TABLE 4 Bundled ACK/NACK # of DL CCs state Modulation Example Mapping; 1(ACKA, ACKB)[1], BPSK (ACKA, ACKB)[1] = (0, 0), (ACKA, NACKB)[1], (ACKA,NACKB)[1] = (1, 0), (NACKA, ACKB)[1], (NACKA, ACKB)[1] = (0, 1), NACK,DTX [NACK = (1, 1), DTX(no Tx)] or [NACK/DTX(no Tx)] 2 (ACKA, ACKB)[k],BPSK/QPSK (ACKA, ACKB)[1] = (00, 0), (ACKA, NACKB)[k], (ACKA, NACKB)[1]= (01, 0), (NACKA, ACKB)[k], (NACKA, ACKB)[1] = (10, 0), NACK, DTX(ACKA, ACKB)[2] = (11, 0), k = 1, 2 (ACKA, NACKB)[2] = (00, 1), (NACKA,ACKB)[2] = (01, 1), [NACK = (10, 1), DTX(no Tx)] or [NACK/DTX(no Tx)] 3(ACKA, ACKB)[k], QPSK (ACKA, ACKB)[1] = (00, 00), (ACKA, NACKB)[k],(ACKA, NACKB)[1] = (01, 00), (NACKA, ACKB)[k], (NACKA, ACKB)[1] = (10,00), NACK, DTX (ACKA, ACKB)[2] = (11, 00), k = 1, 2, 3 (ACKA, NACKB)[2]= (00, 01), (NACKA, ACKB)[2] = (01, 01), (ACKA, ACKB)[3] = (10, 01),(ACKA, NACKB)[3] = (11, 01), (NACKA, ACKB)[3] = (00, 10), [NACK = (01,10), DTX(no Tx)] or [NACK/DTX(no Tx)] 4 (ACKA, ACKB)[k], QPSK (ACKA,ACKB)[1] = (00, 00), (ACKA, NACKB)[k], (ACKA, NACKB)[1] = (01, 00),(NACKA, ACKB)[k], (NACKA, ACKB)[1] = (10, 00), NACK, DTX (ACKA, ACKB)[2]= (11, 00), k = 1, 2, 3, 4 (ACKA, NACKB)[2] = (00, 01), (NACKA, ACKB)[2]= (01, 01), (ACKA, ACKB)[3] = (10, 01), (ACKA, NACKB)[3] = (11, 01),(NACKA, ACKB)[3] = (00, 10), (ACKA, ACKB)[4] = (01, 10), (ACKA,NACKB)[4] = (10, 10), (NACKA, ACKB)[4] = (11, 10), [NACK = (00, 11),DTX(no Tx)] or [NACK/DTX(no Tx)] 5 (ACKA, ACKB)[k], QPSK (ACKA, ACKB)[1]= (00, 00), (ACKA, NACKB)[k], (ACKA, NACKB)[1] = (01, 00), (NACKA,ACKB)[k], (NACKA, ACKB)[1] = (10, 00), NACK, DTX (ACKA, ACKB)[2] = (11,00), k = 1, 2, 3, 4, 5 (ACKA, NACKB)[2] = (00, 01), (NACKA, ACKB)[2] =(01, 01), (ACKA, ACKB)[3] = (10, 01), (ACKA, NACKB)[3] = (11, 01),(NACKA, ACKB)[3] = (00, 10), (ACKA, ACKB)[4] = (01, 10), (ACKA,NACKB)[4] = (10, 10), (NACKA, ACKB)[4] = (11, 10), (ACKA, ACKB)[5] =(00, 11), (ACKA, NACKB)[5] = (01, 11), (NACKA, ACKB)[5] = (10, 11),[NACK = (11, 11), DTX(no Tx)] or [NACK/DTX(no Tx)]

In Table 4, (x, y)[k] indicates ACK/NACK state information x beingtransmitted by using a first PUCCH resource and ACK/NACK stateinformation y being transmitted by using a second PUCCH resource.Therefore, (ACKA,ACKB)[k] indicates that the decoding results of thetransmission block A and the transmission block B received through ak^(th) downlink component carrier respectively corresponds to an ACK.

If there exists a limitation in an uplink transmission power of the userequipment, and, therefore, if only one PUCCH resource can be used at onetransmission point, it is required to reduce the number of ACK/NACKstate information. For example, as shown in Table 4, when the numbers ofdownlink component carriers correspond to 1, 2, 3, 4, and 5, each casemay be respectively indicated by 5, 8, 11, 14, and 17 ACK/NACK stateinformation. In this case, since the user terminal uses only QPSK as themodulation method, and since a total of 9 ACK/NACK state information maybe expressed (or indicated) by using 2 PUCCH resources, a specificnumber of ACK/NACK state information should be bundled so as to beexpressed within the range of 9 ACK/NACK state information.

Therefore, even when bundling the ACK/NACK state information, it ispreferable to bundle ACK/NACK state information that can be generatedrelatively less, as shown in Table 1 and Table 2. Table 5 below shows anexample of reducing the number of ACK/NACK state information shown inTable 4.

TABLE 5 Example Mapping; Note: PUCCH resource is # of DL BundledACK/NACK denoted as rk, where n can be CCs state Modulation 1 to n. 1(ACKA, ACKB)[1], BPSK (ACKA, ACKB)[1] = (ra, 0), (ACKA, NACKB)[1],(ACKA, NACKB)[1] = (ra, 1), (NACKA, ACKB)[1], (NACKA, ACKB)[1] = (rb,0), NACK, DTX [NACK = (rb, 1), DTX(no Tx)] or [NACK/DTX(no Tx)] 2 (ACKA,ACKB)[k], BPSK/QPSK (ACKA, ACKB)[1] = (ra, 0), (ACKA, NACKB)[k], (ACKA,NACKB)[1] = (ra, 0), (NACKA, ACKB)[k], (NACKA, ACKB)[1] = (rb, 00),NACK, DTX (ACKA, ACKB)[2] = (rb, 01), k = 1, 2 (ACKA, NACKB)[2] = (rb,10), (NACKA, ACKB)[2] = (rb, 11), NACK/DTX(no Tx) (ACKA, ACKB)[1] = (ra,00), (ACKA, NACKB)[1] = (ra, 10), (NACKA, ACKB)[1] = (rb, 00), (ACKA,ACKB)[2] = (rb, 01), (ACKA, NACKB)[2] = (rb, 10), (NACKA, ACKB)[2] =(rb, 11), [NACK = (ra, 11), DTX(no Tx)] or [NACK/DTX(no Tx)] 3 (ACKA,ACKB)[k], QPSK (ACKA, ACKB)[1] = (ra, 00), (ACKA, NACKB)[k], (ACKA,NACKB)[1] = (ra, 01), (NACKA, ACKB)[k], (NACKA, ACKB)[1] = (ra, 10),NACK, DTX (ACKA, ACKB)[2] = (ra, 11), k = 1, 2, 3 -- (ACKA, NACKB)[2] =(rb, 00), Merged states (NACKA, ACKB)[2] = (rb, 01), (ACKA, NACKB)[3] =(ACKA, ACKB)[3] = (rb, 10), (NACKA, ACKB)[3] (ACKA, NACKB)[3] = (rb,11), (NACKA, ACKB)[3] = (rb, 11), NACK/DTX(no Tx) 4 (ACKA, ACKB)[k],QPSK (ACKA, ACKB)[1] = (ra, 00), (ACKA, NACKB)[k], (ACKA, NACKB)[1] =(ra, 01), (NACKA, ACKB)[k], (NACKA, ACKB)[1] = (ra, 10), NACK, DTX(ACKA, ACKB)[2] = (ra, 11), k = 1, 2, 3, 4 (ACKA, NACKB)[2] = (rb, 00),Merged states (NACKA, ACKB)[2] = (rb, 01), (ACKA, ACKB)[p] = (ACKA,ACKB)[3] = (rb, 10), (ACKA, ACKB)[q] (ACKA, NACKB)[3] = (rb, 11), (ACKA,NACKB)[p] = (NACKA, ACKB)[3] = (rb, 11), (NACKA, ACKB)[q] (ACKA,ACKB)[4] = (rb, 10), p = 3, 4, q = 3, 4 (ACKA, NACKB)[4] = (rb, 11),(NACKA, ACKB)[4] = (rb, 11), NACK/DTX(no Tx) 5 (ACKA, ACKB)[k], QPSK(ACKA, ACKB)[1] = (ra, 00), (ACKA, NACKB)[k], (ACKA, NACKB)[1] = (ra,01), (NACKA, ACKB)[k], (NACKA, ACKB)[1] = (ra, 10), NACK, DTX (ACKA,ACKB)[2] = (ra, 11), k = 1, 2, 3, 4, 5 (ACKA, NACKB)[2] = (rb, 00),Merged states (NACKA, ACKB)[2] = (rb, 01), (ACKA, ACKB)[p] = (ACKA,ACKB)[3] = (rb, 10), (ACKA, ACKB)[q] (ACKA, NACKB)[3] = (rb, 11), (ACKA,NACKB)[p] = (NACKA, ACKB)[3] = (rb, 11), (NACKA, ACKB)[q] (ACKA,ACKB)[4] = (rb, 10), p = 3, 4, 5 q = 3, 4, 5 (ACKA, NACKB)[4] = (rb,11), (NACKA, ACKB)[4] = (rb, 11), (ACKA, ACKB)[5] = (rb, 10), (ACKA,NACKB)[5] = (rb, 11), (NACKA, ACKB)[5] = (rb, 11), NACK/DTX(no Tx)

In Table 5, since a case where the number of downlink component carriersis more than or equal to 3 occurs less than a case where the number ofdownlink component carriers is less than 3, the bundling of the ACK/NACKstate information starts from the case where the number of downlinkcomponent carriers is less than 3, i.e., the ACK/NACK state informationis expressed with the same resource and modulation value. Therefore, theACK/NACK state of Table 5 is expressed by using 9 ACK/NACK stateinformation.

Hereinafter, when performing ACK/NACK bundling, operations of the userequipment according to the ACK/NACK state information (e.g., when allstates correspond to ACK, when all states correspond to NACK, when allstates correspond to DTX, and when partial states correspond to ACK,i.e., number information of ACK).

Firstly, a general operation of the base station and user equipmentaccording to the HARQ method will be described as follows. After thebase station transmits a control channel to the user equipment, the basestation transmits a data channel depending upon the control channel.When the control channel has been successfully received, the userequipment receives the data channel so as to attempt decoding. Once theuser equipment successfully performs decoding of the data channel, anACK signal is generated. However, if the user equipment fails to performdecoding, an NACK signal is generated. More specifically, when the userequipment fails to receive the control channel, i.e., in a DTX state,ACK/NACK signals are not transmitted, and depending upon the success orfailure in the decoding of the data channel, an ACK or NACK signal istransmitted to the base station.

When the base station receives an ACK from the user equipment, the basestation performs a new transmission, and when the base station receivesan NACK from the user equipment, the base station performsretransmission. Also, in a DTX state, a new transmission is performed.

Hereinafter, the operations of a base station and a user equipment usingACK/NACK bundling according to the present invention will now bedescribed. However, during carrier aggregation (or bandwidthaggregation), the control channel and the data channel may beindependently scheduled and transmitted for each component carrier orregardless of the component carrier.

Firstly, the base station transmits a control channel to the userequipment and, then, transmits a data channel depending upon the controlchannel. Herein, the control channel signifies control channel relatedto one or more data channels, which are scheduled to multiple downlinkcomponent carriers. And, each of the control channels may be processedwith Joint Coding or processed with Separate Coding. Also, the datachannel may be independently transmitted through multiple downlinkcomponent carriers.

If the control channels are processed with Joint Coding, and when thecontrol channel reception is successful, the user equipment receives thedata channel, and when the control channel reception is failed, the userequipment does not receive the data channel.

However, if the control channels are processed with Separate Coding, andwhen the control channel reception is successful, the user equipmentreceives the data channel. And, when the decoding of all data channelsis successful, an ACK signal is transmitted. However, when decoding ofeven one data channel is failed (or unsuccessful), a NACK signal istransmitted. Also, when control channel reception is failed, the datachannel is not received and no response is transmitted (i.e., DTX).

Accordingly, when the control channels are processed with SeparateCoding, and when the user equipment bundles the ACK/NACK/DTX signals foreach downlink data channel, so as to transmit the state information, theuser equipment cannot identify (or differentiate) the case wherein theuser equipment cannot receive a specific control channel and, therefore,has a DTX, and wherein decoding of the remaining data channels is allsuccessful, thereby transmitting an ACK, and the case wherein allcontrol channels are normally received without any DTX, and whereindecoding of all data channels is also successful, thereby transmittingan ACK. Therefore, such problems may be resolved by using thetransmission of information on the number of ACKs according to thepresent invention.

More specifically, when the base station receives an ACK for all datachannels transmitted from the user equipment, the base station performsa new transmission. Also, when a NACK is received in the A/N informationtransmitted from the user equipment, retransmission may be performed.However, all data channels that were transmitted during the initialtransmission are all retransmitted.

However, when ACK is received for some of the data channels, i.e., whenthe number of data channels during the initial transmission from thebase station is different from the number of ACKs received from the userequipment, the base station may either perform a new transmission of alldata channels or perform retransmission.

When the base station selects new transmission, since the user terminalhas already transmitted ACKs in accordance with the decoding result ofthe previous transmission, the user terminal may regard the newlyreceived data channels as a completely new set of data channels.

If the base station select retransmission and performs transmissionaccordingly, the user equipment is not required to perform additionaldecoding on the data channels for which the user equipment hadpreviously transmitted ACKs. Nevertheless, the user equipment should beable to perform blind decoding on the remaining data channels. In orderto do so, it is preferable that the user equipment stores the subframes,on which the previous decoding was performed, in a buffer until the userequipment receives new data indication from the base station.

Alternatively, when the respective subframes are not stored in thebuffer, the user equipment may simply perform decoding only on thecurrently received PDSCH in accordance with the retransmission controlchannel information.

Meanwhile, when the separately coded PDCCH is received for each downlinkcomponent carrier, and when there is not means for knowing the number ofthe received PDCCHs, a method of notifying the number of ACKs via uplinkshould be performed, as described in the method proposed above.

However, when information indicating the number of scheduled PDSCHsexisting in the downlink component carrier is included through thedownlink control channel, the user equipment may perform ACK/NACKbundling in accordance with the indicated number. More specifically,when the number of downlink component carriers including the scheduledPDSCHs can be known through the downlink control channel, the userequipment is not required to feed-back information on the umber of ACKsvia uplink.

In this case, when the number of actually decoded PDSCHs is differentfrom the number of downlink component carriers including the scheduledPDSCHs indicated by the base station, the user equipment shall transmita NACK without exception. Also, when an error exists in the decodedPDSCH, a NACK is transmitted. Also, when the number of actually decodedPDSCHs is equal to the number of downlink component carriers includingthe scheduled PDSCHs indicated by the base station, and when there is noerror in the decoded PDSCH, the user equipment transmits ACK.

Therefore, depending upon a case wherein the number of downlinkcomponent carriers including the scheduled PDSCHs is received throughthe downlink control channel, bundling may be performed as 1) a simplebundling to ACK, NACK, DTX, or 2) a bundling to ACK+number of decodedPDSCHs, NACK, DTX. Additionally, bundling may also be performed as 3) abundling to ACK+number of decoded PDSCHs, NACK+number of decoded PDSCHs,DTX. Alternatively, when the number of scheduled PDSCHs (or number ofPDSCHs) is notified or can be known, the ACK, NACK, DTX are not bundledand may each be transmitted in accordance with a pre-decided ACK/NACKtransmission format. At this point, depending upon the number ofrequired bits, transmission may be performed by using multiple PUCCHresources, or transmission may be performed by selecting a specificPUCCH resource from the multiple PUCCH resources. Also, in this case, bydefining a PUCCH format 2 type or a new PUCCH format, a format oftransmitting only a designated number of ACK/NACK/DTX may be available.

Depending upon such bundling methods, the number of PUCCH resources thatcan send ACK/NACK may be automatically decided and used, or the PUCCHformat may be modified and used. In case information indicating thenumber of scheduled PDSCHs is included in the PDCCH, when the userequipment transmits ACK, it may be estimated that the data beingtransmitted from the base station at a specific transmission pointcorrespond to new data. When the user equipment transmits NACK, it maybe estimated that a new data indicator is received or thatretransmission will be performed.

At this point, when a new data indicator is received, the user equipmentperforms decoding through Chase Combining. And, when a retransmissioncontrol information is received, the user equipment may simultaneouslyperform Incremental Redundancy and decoding through Chase Combining.

FIG. 12 illustrates an exemplary base station and an exemplary userterminal that can be applied to the embodiment of the present invention.

Referring to FIG. 12, a wireless communication system includes a basestation (BS, 1210) and a user equipment (UE, 1220). In a downlink, thetransmitter corresponds to a portion of the base station (1210), and thereceiver corresponds to a portion of the user equipment (1220). In anuplink, the transmitter corresponds to a portion of the user equipment(1220), and the receiver corresponds to a portion of the base station(1210).

The base station (1210) includes a processor (1212), a memory (1214),and a Radio Frequency (RF) unit (1216). The processor (1212) may beconfigured to realize procedures and/or methods proposed in the presentinvention. The memory (1214) is connected to the processor (1212) andstores diverse information related to the operation of the processor(1212). The RF unit (1216) is connected to the processor (1212) andtransmits and/or receives radio signals. More specifically, the RF unit(1216) includes a transmitting module and a receiving module.

The user equipment (120) includes a processor (1222), a memory (1224),and an RF unit (1226). The processor (1222) may be configured to realizeprocedures and/or methods proposed in the present invention. The memory(1224) is connected to the processor (1222) and stores diverseinformation related to the operation of the processor (1222). The RFunit (1226) is connected to the processor (1222) and transmits and/orreceives radio signals. More specifically, the RF unit (1226) includes atransmitting module and a receiving module.

The base station (1210) and/or the user equipment (1220) may have asingle antenna or multiple antennae.

The aforementioned embodiments are achieved by combination of structuralelements and features of the present invention in a predetermined type.Each of the structural elements or features should be consideredselectively unless specified separately. Each of the structural elementsor features may be carried out without being combined with otherstructural elements or features. Also, some structural elements and/orfeatures may be combined with one another to constitute the embodimentsof the present invention. The order of operations described in theembodiments of the present invention may be changed. Some structuralelements or features of one embodiment may be included in anotherembodiment, or may be replaced with corresponding structural elements orfeatures of another embodiment. Moreover, it will be apparent that someclaims referring to specific claims may be combined with another claimsreferring to the other claims other than the specific claims toconstitute the embodiment or add new claims by means of amendment afterthe application is filed.

The embodiments of the present invention have been described based onthe data transmission and reception between the base station and theuser equipment. A specific operation which has been described as beingperformed by the base station may be performed by an upper node of thebase station as the case may be. In other words, it will be apparentthat various operations performed for communication with the userequipment in the network which includes a plurality of network nodesalong with the base station can be performed by the base station ornetwork nodes other than the base station. The base station may bereplaced with terms such as a fixed station, Node B, eNode B (eNB), andaccess point. Also, the terminal may be replaced with terms such as UE(User Equipment), MS (Mobile Station), and MSS (Mobile SubscriberStation).

The embodiments according to the present invention can be implemented byvarious means, for example, hardware, firmware, software, or theircombination. If the embodiment according to the present invention isimplemented by hardware, the embodiment of the present invention can beimplemented by one or more ASICs (application specific integratedcircuits), DSPs (digital signal processors), DSPDs (digital signalprocessing devices), PLDs (programmable logic devices), FPGAs (fieldprogrammable gate arrays), processors, controllers, microcontrollers,microprocessors, etc.

If the embodiment according to the present invention is implemented byfirmware or software, the embodiment of the present invention may beimplemented by a type of a module, a procedure, or a function, whichperforms functions or operations described as above. A software code maybe stored in a memory unit and then may be driven by a processor. Thememory unit may be located inside or outside the processor to transmitand receive data to and from the processor through various means whichare well known.

It will be apparent to those skilled in the art that the presentinvention can be embodied in other specific forms without departing fromthe spirit and essential characteristics of the invention. Thus, theabove embodiments are to be considered in all respects as illustrativeand not restrictive. The scope of the invention should be determined byreasonable interpretation of the appended claims and all change whichcomes within the equivalent scope of the invention are included in thescope of the invention.

INDUSTRIAL APPLICABILITY

The present invention may be applied in a wireless communication system.More specifically, the present invention may be applied to a method andapparatus for transmitting ACK/NACK information in a wirelesscommunication system applying carrier aggregation (or bandwidthaggregation).

The invention claimed is:
 1. A method for receiving ACK/NACK(Acknowledgement/Negative-ACK) state information in a wirelesscommunication system, the method comprising: transmitting multipletransmission blocks through multiple downlink component carriers to auser equipment (UE); and receiving multiple transmission block ACK/NACKstate information through a single uplink component carrier from the UE,wherein the multiple transmission block ACK/NACK state informationindicates a number of ACK responses among ACK/NACK responsescorresponding to each of the multiple transmission blocks.
 2. The methodof claim 1, wherein the multiple transmission block ACK/NACK stateinformation further indicates a case where decoding procedures of themultiple transmission blocks are all failed at the UE.
 3. The method ofclaim 1, wherein transmitting the multiple transmission blockscomprises: transmitting two or more transmission blocks through at leastone downlink component carrier among the multiple downlink componentcarriers.
 4. The method of claim 1, wherein receiving the multipletransmission block ACK/NACK state information comprises: receiving themultiple transmission block ACK/NACK state information by using one ormore PUCCH (Physical Uplink Control CHannel) resources included in theone uplink component carrier.
 5. The method of claim 1, wherein themultiple transmission block ACK/NACK state information is modulated byusing QPSK (Quadrature Phase Shift Keying).
 6. A base stationcomprising: a transmitting module for transmitting multiple transmissionblocks through multiple downlink component carriers to a user equipment(UE); and a receiving module for receiving multiple transmission blockACK/NACK (Acknowledgement/Negative-ACK) state information through asingle uplink component carrier from the UE, wherein the multipletransmission block ACK/NACK state information indicates a number of ACKresponses among ACK/NACK responses corresponding to each of the multipletransmission blocks.
 7. The base station of claim 6, wherein themultiple transmission block ACK/NACK state information further indicatesa case where decoding procedures of the multiple transmission blocks areall failed at the UE.
 8. The base station of claim 6, wherein thetransmitting module transmits two or more transmission blocks through atleast one downlink component carrier among the multiple downlinkcomponent carriers.
 9. The base station of claim 6, wherein thereceiving module receives the multiple transmission block ACK/NACK stateinformation by using one or more PUCCH (Physical Uplink Control CHannel)resources included in the one uplink component carrier.
 10. The basestation of claim 6, wherein the multiple transmission block ACK/NACKstate information is modulated by using QPSK (Quadrature Phase ShiftKeying).